Slant six compression

The advertised CR may be 8.4:1 but not for real.

We milled our /6 head .050" at last January's rebuild, and with stock .040" over pistons, we got 130 psi across all cylinders, and that is at or slightly above FSM numbers. (I did forget to prop the carburator open so it could be a bit higher.) So if you got 140 psi then that is good; it could have had the head shaved. Or, the compression gauge may not be totally accurate, or they did not run the compression test 'dry' and put oil in the cylinders to make the rings seal better! Either way, it sounds like it has decent cylinder sealing; if you have doubts, ask for a cylinder leakdown test.